1. Field of the Invention
The invention relates to a device for reducing one or more resonant vibrations of rotor blades in turbomachines, means for the selective disturbance of the flow being arranged between the rotating blade tip and that wall of the casing which bounds the flow duct. It also relates to a method for constructing and operating the device.
In turbomachines such as turbines, compressors, turbopumps and fans both of the axial-flow and of the radial-flow type, the rotor blades are excited into vibrations by irregularities in the flow. If the speed or the speed multiples of the rotor coincide with the natural frequency of a rotor blade, resonant vibrations and hence high mechanical stresses can arise which can shorten the life of the blades in an impermissible manner. In the case of machines with a variable speed, the occurrence of resonances must be expected at any time. However, even in the case of machines with a constant operating speed, the resonance speeds are generally so low that several resonances have to be passed through during starting and stopping.
2. Discussion of Background
Known devices for reducing vibrations are the customary damping wires, which limit the vibration amplitudes by binding the blades. Shroud plates or shroud bands are also used. Such measures are generally associated with efficiency losses and/or are costly.